1. Field of the Invention
The present invention relates to a cooling air guiding apparatus, and particularly relates to a cooling air guiding apparatus for cooling a lamp in a projection apparatus.
2. Descriptions of the Related Art
Projection apparatuses are widely used for meetings, entertainment and studying activities. To meet the various needs of users, projection apparatuses often need to be installed in different locations and orientations. For example, a projection apparatus that is used in a meeting room or a classroom is typically suspended from the ceiling upside down, which may dispense with bothers of removing the projection apparatus and further save available spaces on the ground. However, because hot air always rise upwards, the temperature of the space above the lamp of the projection apparatus will go higher than that of the space below the lamp during operation. Once the temperature difference gets excessively large, the lamp may burst. As a result, projection apparatuses currently available adopt a side-air-intake design to cool the lamp in expectation of lowering the temperature difference in the vertical direction.
However, as shown in FIG. 1, a projection apparatus 1 often needs to be installed in a non-horizontal orientation to adapt to the concrete circumstances. For instance, when the target position of the projected images needs to be elevated and it is difficult to move the projection apparatus 1 backwards, an elevated angle between the projection direction of the lens 11 and a level flat of the projection apparatus 1 may be adjusted to be slightly higher so that the images are projected at the elevated angle θ. As a result, even though the opening position where a cooling air flow 10 flows into the lamp remains unchanged, the path of the cooling air flow 10 moves downwards, with most of the cooling air flow 10 passing the lower portion of the lamp 13. Consequently, the heat accumulating on the upper portion of the lamp 13 can degrade the performance as well as lead to the premature failure of the lamp 13. This imposes a great restriction on the installation orientation of the projection apparatus.
To avoid the excessively large temperature difference and high heat accumulation at some installation orientations, a great restriction is imposed on the installation orientations of projection apparatuses. On the other hand, if the projection apparatus is installed in an undesired orientation, it further affects the normal heat dissipation for other elements adjacent to the lamp. To solve this problem, manufacturers have proposed a cooling structure 2 for cooling the lamp 20 by changing the air flowing direction and the flow rate of a cooling air flow to appropriately dissipate the heat generated by the lamp 20. A cross-sectional view of the cooling structure 2 is depicted in FIG. 2A.
The cooling structure 2 has a cooling fan 21, an opening 23, a pair of air guiding passages 25 and a movable baffle 27. An upper end of the movable baffle 27 is disposed at the opening 23 with a pivot 271, so that a cooling air flow generated by the fan 21 and entering the opening 23 is separated into a left and a right air flow before going into the air guiding passages 25. The air guiding passages 25 are disposed on both sides of a lamp shade 201 respectively, so that the cooling air can flow towards a lamp wick 203 along an interior side of the lamp shade 201 and carry the heat generated by the lamp wick 203 outwards.
Generally, the light exits the lamp 20 in a direction perpendicular to the projection direction 22. Therefore, when the projection apparatus is tilted upwards or downwards at an elevated angle between the projection direction 22 of the lens and the level flat, the movable baffle 27 will be slanted to the left or to the right due to the gravity thereof, which may lead to an unequal cooling air flow on both sides. For example, as shown in FIG. 2B, if the projection apparatus is tilted upwards at the elevated angle between the projection direction 22 of the lens and the level flat, a lower side of the movable baffle 27 is slanted to the right to cause a large intake flow at the left opening 23a than that at the right opening 23b. In this case, the two air guiding passages 25 corresponding to the left opening 23a and the right opening 23b also have their locations moved upwards and downwards respectively. The larger cooling air flow passes the upwards displaced air guiding passage 25 into the lamp 20, while the smaller one passes the downwards displaced air guiding passage 25 into the lamp 20 for cooling. Due to the rising hot air, the space above the lamp 20 is cooled by a larger air flow, thus obtaining a more significant cooling effect.
In this structure, the orientation of the rotatably movable baffle 27 can be changed under the action of the gravity to adjust the cooling air flow, however, the cooling air from the fan 21 can affect the stationary status of the movable baffle 27 when the projection apparatus is fixed in a certain orientation, causing the continuous swaying of the movable baffle 27. As a consequence, it is difficult to correctly control the cooling effect on the lamp 20 under the various orientations of the projection apparatus.
In summary, because the cooling scheme of prior art lamps has not been perfected yet, a restriction is imposed on the installation orientation of the projection apparatus, making it difficult to dispose the projection apparatus in an optimum orientation. In other words, the user is not allowed to install the projection apparatuses in any orientation as desired. Furthermore, because the aforesaid cooling scheme has dual cooling air passages plus a movable baffle, it is difficult to correctly control the cooling air flow due to the swaying of the baffle under action of the air flow.
In view of this, it is highly desirable in the art to provide a cooling air guiding apparatus that can overcome the above disadvantages and to also provide a projection apparatus with such a cooling air guiding apparatus.